Feeding means for molding presses



Dec'. 30, 1941. w ERNST Er AL 2,268,026

FEEDING MEANS FOR MOLDING PRESSES Original Filed April 26, 1937 4Sheets-Sheet 1 ATTORNEYS Dec. 30, 1941. w. ERNST ETAL 2,268,026

FEEDING MEANS FOR MOLDING PRESSES original Filed Apri12e, 1957 4sheets-sheet 2 69 13 92 a9 @lg a /NVENTORS WALTER ERNST IRA B. LAWYERATTORNEYS Dec. 30, 1941. w. ERNST Erm.

FEEDING MEANS FOR MOLDING PRESSES Original Filed April 26, 1937 4Sheets-Sheet 3 QuTR vr u TRW, R NEU 0 T @.MBST mm Q5 MN Dec. 3o, 1941.w. ERNSf mL 2,268,026

FEEDING MEANS FOR MoLDING PRESSES original Filed April 26, '1937 4sheets-sheet 4 /47 /NVEA/Tons VALTER ERNST RA B. LA wYL-R /35 /23 "Y .UATTORNEYS vfrom the feeding screw so as to enable the Patented Dec. 30,1941 UNITED STATESA PATENT OFFICE FEEDIN MEANS FOR MOLDING PRESSESWalter Ernst and Ira B. Lawyer, Mount Gilead, Ohio, assignors to TheHydraulic Press Corp.- Inc., Wilmington, Del., a corporation of Dela-Ware Original application April 26, 1937, Serial No.

Divided and this application October 12, 1937, Serial N0. 168,614

10 Claims.

screw for positively feeding the plastic materialy into the injector.

Another object is to provide a plastic extrusion molding machine,wherein the positive feeding screw is actuated by a motor, which inturn, is responsive to the operation of limit switches actuated by theinjection plunger and controlled by timing means in such a manner as tocause a predetermined amount of plastic material to be fed into theinjector.

Another object is to provide a motor-operated feeding mechanism, asdescribed in the lpreceding paragraph, wherein the motor and limitswitches cooperate to feed slightly more than the necessary amount ofplastic material into the injector,

and automatically skip a feeding stroke when an excess of materialgathers within the injector, thereby insuring that an adequate supply ofmaterial is always present for injection by the injector.

Another object is to provide a feeding mechanism for a plastic extrusionmolding machine, this mechanism employing a feeding screw actuated bygearing from a motor unit in such a manner that the motor unit may bereadily detached easy cleaning of the feeding screw.

Another object is to provide a feeding mechanism, asA described in thepreceding paragraph, wherein a shear pin is provided in the feedingscrew mechanism so as to shear ofi' in the event of jamming of themachine, and thereby to prevent breakage of other parts of the machine.

This is a division of our copending application, Ser. No. 138,904, filedApril 26, 1937.

In the drawings:

Figure 1 is a substantially horizontal section through the plasticextrusion molding machine of this invention, showing the hydrauliccircuit.

Figure 2 is an enlarged view of the right-hand end of the machine shownin Figure 1.

Figure 3 is a vertical section along the line 3-3 in Figure 2, showingthe feeding mechanism for the injection material.

Figure 4 is a cross section through the forward end of the injection orextrusion chamber, taken along the line 4--4 in AFigure 3.

Figure 5 is a cross section through the rearward end of the injection orextrusion chamber,

showing the cooling passages for preventing the premature softening ofthe plastic material, taken along the line 5-5 in Figure 3.

Figure 6 is a wiring diagram showing the electrical elements and circuitfor actuating the feeding mechanism.

Figure 7 is a simplified wiring diagram of the feed-actuating circuitshown in Figure 6.

General arrangement plungers into engagement with the other, one iplunger providing a booster or rapid traverse -speed and the otherproviding a slower vor more powerful clamping effect. The other die ismounted upon cushioning plungers which are separable from cushioningpistons, the latter not being engaged until the plungers have moved backa predetermined distance. A hydraulic circuit 1s arranged to controlthese various hydraulic elements (shown in Figure 1). The feeding andinjecting mechanism shown in Figure 3, and on a smaller scale in Figure1, consists of a heated injection chamber having a power-operatedfeeding screw for feeding the granular plastic material into theinjector. The feeding screw is operated by a motor which is timed by atiming device, the latter in turn being controlled by the actuation oflimit switches operated in response to the reciprocation of theinjection plunger.

Molding machine construction The molding machine portion is shown inFigure 1, in diagrammatic form, certain of the purely mechanical andframe elements being omitted for elearness of showing. The moldingportion consists, in general, of strain rods I0 having cross members Il,i2 and I3, xedly mounted thereon from left to right. The strain rods il)also serve to guide the die carrier i4 and die head I5 in theirreciprocating motion, as hereinafter described in detail.

Mounted upon the cross member li is a hydraulic cylinder i6 with aninwardly extending hollow plunger il mountedl in the outer end thereof,and secured thereto as by the nut IB. The hollow plunger Il is providedwith a bore I9. The cylinder i6 is provided with a bore 20, within whichreciprocates a main plunger 2|, of doubleacting form, and having aninternal bore 22 therein. The bore 22 serves as a cylinder bore forreceiving the hollow plunger Il, and commumcation therewith isestablished through the hollow bore i9 in the hollow plunger l1. The

I hollow plunger |1 cooperates with the internal On the right-hand endof the'main plunger 2| is mounted the die carrier I4, the latter havingthreaded sockets 23 for the reception of the threaded limit rods 24,having heads 25 on the opposite ends thereof. The limitrods 24 serve toengage the cross member and limit the stroke of the die carrier I4 andmain plunger 2| in the event that the dies are omitted and the machinestarted while in that condition. The cylinder bore 20, at its outer end,is provided with a packing 26, compressed by a gland 21 for preventingthe escape of ud around the main plunger 2|.

Mounted on the die carrier I4 is a die support 28 carrying a die 29,which forms one-half of a die assembly, the other half consisting of theoppositely disposed die 30. The die support 28 is provided with achannel 3| for receiving the knock-out bar 32, actuated by .the rods 33connected to the ends thereof when these rods engage the cross member IIon the return stroke of the main plunger 2|, after the completion of amolding operation. The pins 34 are mounted on the knock-out bar 32 andpass through the holes 35, into the die cavities 36 of the die 29, whenthe knock-out position is reached (Figure 1). Adjustable stops 31,mounted on the strain rods I0, serve to engage the die carrier I4 andprevent it and the main plunger 2| from traveling further to the leftthan is required to open the dies 29 and 30 and eject the moldedarticle. This arrangement saves time in openingand, closing the dies 29and 30.

The die 30 is mounted upon a die support 38 (Figures 1 and 2), bothbeing bored centrally to admit an injection tube 39 having an injectionsocket 40 at its right-hand end. The die support 38 is mounted upon thedie head I5, which as previously stated, is slidably mounted for.guidance along the strain rods l0. The die head I is centrally providedwith an aperture 4|, permitting the injection mechanism to approach andengage the socket 40. The die head is bored to receive bolts 42, thethreaded ends o f which are threaded into cushioning rods 43 engagingsockets 44 in the die head I5. The opposite ends of the cushioning rods43 pass through bores 45 in the cross member I2, and likewise throughbores 46 in the cross member I3, terminating in the cylinder bores 41.The bores 46 are closed by packings 48'and 49, compressed by the glands50.

The right-hand ends of the cushioning rods 43 are enlarged, as at 5|,and engage cushioning pistons 52, but are not otherwise connectedthereto. The cushioning pistons 52 are movable independently of thecushioning rods 43, and reciprocate within cylinder bores 53 which arecoaxial with and substantially form enlargements of the cylinder bores41. The outer ends of the cylinder bores 53 are closed by an end plate54 having ports 55 therein for the admission of pressure uid to thecylinder bores 53. Similarly, the cylinder bores 41 are provided withports 56 for a similar purpose. The end plate 54 is provided with acentral port 51, serving to admit pressure fluid to a central cylinder58, within which a piston head 59 reciprocates. The piston head 59 isbored to receive a. piston rod 60, secured thereto by the nut 6|threaded upon the right-hand end thereof. A port 62 serves for theadmission and discharge of iluid from the opposite end of the cylinderbore 58. Packings 63 and 64, closed by the gland 65, serve to preventthe escape of fluid around the piston rod 60.

On the piston rod 60 is'mounted anv annular cam'66 for actuating certainlimitswitches, hereinafter described. To the left of the cam 66 thepiston rod 60 is reduced in diameter to form an injection plunger 61,which passes through a sleeve 68 mounted in the bore 69 of the crossmember I2, and terminating at its opposite end in a bore 10 of aninjector, generally designated 1|. Beyond the bore 10. the injector isenlarged to form a chamber 12, containing the bored supporting portion'13 of a spindle-shaped diverting member 14 for diverting the plasticmaterial therearound. Beyond the member 14 the injector chamber 12 isthreaded, as at 15, to receive a nozzle 16 having a conical wall 11 andan outlet passage 18. The nozzle 16 is also provided with a protuberance19 of corresponding conguration to the socket 40, and adapted to matetherewith when the die head I5 and die support 38 are moved intoengagement therewith.

The injector 1| is provided with radiating ns 80, arranged within aheating chamber 8| having a cylindrical wall 82 with a port 83therethrough (Figure 2). The Wall 82 is surrounded by a heat-insulatinglayer 84 for retaining the heat within the chamber 8| The injector 1| isheated by a suitable fluid, such as hot oil, admitted thereto throughthe port 83 and discharged through the opposite port 85, at the oppositeend thereof. The injector 1| is provided with a flanged portion 86,engaging a heat-insulating disc 81, which in turn, engages the ilangedportion 88 of the cross member I2. This flanged portion 88 is joined toa neck portion 89 containing an annular chamber 90, with entrance andexit ports 9| -and 92. The purpose of this chamber 90 is to provide forthe circulatlon of cooling fluid to prevent the premature softening ofthe plastic material and the consequent clogging of the feedingmechanism, hereinafter demission of heat from the flanged portion 86 ofthe anged portion 88.

Feeding mechanism The feeding and injection mechanisms are shown inenlarged detail in Figure 3. The sleeve 68 is provided with an aperture93, aligned with the mouth of an inclined feedingl cylinder bore 94within the cross member I2. An inlet passage 95 opens into the upper end4of this bore 94, and serves to carry the granulated plastic moldingmaterial thereto from the hopper 96. The latter is provided with a cover91, hinged as at 98. Mounted for rotation inthe cylinder bore 94 is afeeding screw 99, connected by the shear pin |00 within the socket |0|of the shaft |02 (Figure 3). The latter is mounted upon anti-frictionbearings |03-and |04 and carries a bevel gear |05, meshing with asimilar bevel gear 06 upon the cross shaft |01 leading into the gear box|08 of the motor |09. The gears |05 and |06 are arranged within a casingH0, mounted upon the bracket I, which in turn is secured to the crossmember I2. The bored plate ||2 serves ,to close the casing ||0 andsurrounds the shaft |02, the escape of fluid being prevented by thepacking ||3.

The motor |09 and gear box |08 form a reduction unit, together with theshaft |01 and bevel gear |06, and are separable from the casing towhichA they are bolted. The bevel gears and |06, together with theconstruction of the motor |09 and gear box |03, previously described,serve to permit the placing of the motor |09 in a convenient positionfor mounting and also make it possible to remove the .screw assemblywithout disturbing the motor.

Mounted upon a bracket ||4, secured to the lower portion of the crossmember |2 (Figure 3), is a sliding plate IIB* which may be moved to theright or to the left in order to adjust :its position. Mounted upon thebracket ||4 is a limit switch ||5, a second limit switch ||6 beingmounted upon the sliding plate IIG. The limit switches ||5 and ||6 areprovided with rollers ||1 and ||9 for' actuating and closing theswitches when they are engaged by the cam 66. The switches ||5 and ||6are of a normally open type, which close the circuit when their rollers||1 and ||3 are depressed. The electrical connection of these limitswitches is subsequently to be described. The operation of the machineas a whole will be discussed after the description I'he feed-operatingcircuit (Figures 6 and '7) includes a five-pole motor starting switch|20, a timing switch |2|, a two-pole magnetic contactor switch 22 andthe limit switches ||5 and ||5. The timing switch |2| has a timing motor|23 which, after an adjustably variable predetermined time, opens thecontacts |25 and |26 of the main contact assembly |24 on the switcharms,|21 and |28. A coil |29 operates a clutch (not shown)interconnecting the timing motor |23 with the contact operativemechanism. The auxiliary contact assembly |30, with contacts |3| and |32on arms |33 and |34, is opened by the motor |23 at the end of apredetermined maximum time cycle, and protects the circuit in the eventof the failure of the contact assembly |24 to open.

The five-pole motor starting switch conltains iive switch blades |35 to|39, inclusive,

mounted upon an armature rod |40 adapted to be operated by the operatingcoil |4| when the latter is energized. The switch blade |39 serves as aninterlock or holding switch so as to maintain the energization of theoperating coil |4| when the limit switch ||5 is opened, after itsrelease by the cam 66. Theswitch blades |35, |31 and |36 serve toconduct electricity from the power lines |42, |43 and |44 to the feedingmotor |09. The two-pole magnetic contactor `switch |22 is provided withan operating coil |45,

which when energized is adapted to close two normally open switch blades|46 and |41, respectively. The switch blade |41 serves as an interlockswitch for closing the holding circuit to maintain the energization ofthe operating coil |45 when the second limit switch ||6 is opened afteritsrelease by the cam 66.

In the operation of the electrical control system, let it be assumedthat the injecting plunger 61 executes an injection` stroke andconsequently moves the cam 66 into engagement with the roller ||9(Figure 3), and closes the second limit switch ||6. When this occurs(Figure 7), the operating coil |45 of the two-pole magnetic contactorbecomes energized through the timing switch assembly |24 and from theline |43 to the line |44. With the closing of the magnetic contacterswitch |22, the switch blade |41 thereof likewise closes, and completesa holding circuit for the operating coil |45, even when the limit switch||5 is released by the return stroke of the plunger. As the plungerreturns to its retracted position, the cam 66 depresses the roller ||,1of the limit switch H5, and causes the circuit to be closed between thelines |43 and |44 by way of the previously closed magnetic con- -tactorblade |46, the limit switch ||5 (Figure 7), the operating coil 4| of themotor starting switch |20 and the contacts |24 of the timing switch |2|.The coil |4|, thus energized, causes the motor starting switch |20 toclose so that its ilve switch blades interconnect their correspondingpoles. The closing of the switch blade |35 serves to energize the timingmotor |23 of the timing switch |2|, and causes it to begin its cycle ofoperations. The closing of the switch blades. |35, |31 and |38 causesthe feeding motor |09 to be energized from the power lines |42, |43 and|44. 'Ihe closing of the final switch blade |39 operates a holdingcircuit to maintain the coil |4| in an energized condition, even whenthe limit switch ||5 is released.

After theelectrical timing switch |2| has run its course for thepredetermined time for which it has been set, the circuit is opened atthe timing switch contacts |24 (Figure 7). This action deenergizes theoperating coils |4| and |45 of the motor starting switch |20 andmagnetic contactor switch |22, causing the switch blades of bothswitches to disengage their respective contacts and open the circuitscontrolled thereby. The consequent opening of the magnetic contactorswitch blade |35 (Figure 7) deenergizes the timing motor |23 and resetsthe timing device for another cycle of operations. This cycle ofoperations is repeated when the injection plunger executes anotherworking stroke and returns to its original position, thereby againactuating the limit switches ||5 and |6.

Under these conditions the timing switch has been so adjusted that themotor will run for a suiiicient length of time to inject into thechamber 10 slightly more than the correct amount of material. Thisslight over-feeding prevents a scarcity of material and accordingly theinjection plunger 51, after several strokes, is incapable of Acompletinga working stroke on account of the piling up of material within the boreor chamber 10. When this happens the cam 66 does not move sufficientlyfar to the left to close the limit switch ||6 so that the circuit whichenergizes the magnetic contactor switch |22 is not completed. When theplunger returns to its starting position and the cam 66 closes the limitswitch H5, under such conditions no energization of the operating coils|4| and |45 takes place, hence, the motor |09 fails to operate toactuate the feed screw 99. On the next stroke of the plunger 61 theexcessive quantity of material will be injected into the dies, therebyrelieving the surplus quantity in the injection bore 10. 'I'he plunger61 then travels sufllciently far to the left to close the limit switch||6, and the complete cycle of operations is again carried out.

Hydraulic circuit 'I'he central bore |9 of the booster plunger |1 isprovided with an outlet port |50, from which a pipe |5| runs to adie-clamping valve |52 (Figure l). From the pipe |5| a branch |53 runsto a platen-operated valve |64, fromlwhich runs to a check valve |59, aline |66 continuing therefrom to the oil reservoir or tank |6|. Thecheck valve |59 is provided with a chamber |62 within which a pawl |63engages a seat |64 to permit the flow of uid solely in the direction ofthe reservoir |6| to the main cylinder bore 26. From the line |5| abranch line |65 runs to a leakage pump |66, the suction line |61therefrom running to the tank |6|.

'From the piston .valve |52 the pressure line |68 runs to the main pump|69, the suction line |16 running therefrom to the tank |6|. Thepressure line |68 contains a check valve |1| for permitting theilow ofiiuid solely in the direction from the pump |69 to the valve |52, andnot in the reverse direction. From the valve |52 the line |12 Vruns to aport |13 leading into the opposite end of thev main cylinder 26 from theport |56.` A branch line |14 with a manually operated valve |15 runsfrom the line |12 tothe port 56 in the cylinder bores 41, therebyadmitting and discharging fluid from the space to the left of thepistons 52. Similarly, a line |16 runs from the line |68 immediatelypreceding the check valve |1| to the ports 55 in the cylinder bores 53,thereby admitting or discharging fluid to and from Ythe space to theright of the pistons 52. 30

An oil line |11 runs by way of a heater (not shown) to the heatingchamber 8| of the injector 1|, and to a second line |16 conveying fluid'away from this chamber. Cooling conduits |19 and |86 serve to convey acooling fluid to and from 'the cooling passage 96, around th entrance tothe injection chamber 16. Running from the valve |52 is a line |8|leading to the injector operating valve |82. A line |83 with a manuallyoperated valve |84 serves to interconnect the lines |14 and |6|. Fromthe valve |82v the lines |65 and |86 run to the ports 62 and 51,respectively, on the left and righthand sides of the injector piston 59.The remaining line v|81 runs from the injector operating valve |82 tothe line |68 on the opposite side of the check valve |1| from thedie-clamping valve 52.

General operation In order to start the operation of the machine byclamping the dies 29 and 36 together, the hydraulic pumps |66 and |69are started in operation, thereby generating fiuid pressure which istransmitted to the lines- |65 and |68, respectively. The die-clampingvalve |52, which is preferably of the piston type, is shifted by theoperator so that uid passes from the line |68, through the check valve|1| and out the line |5|, Where it is augmented by pressure fluid fromthe leakage pump |66. The fluid continues onward and enters the port|56, proceeding into the bore |9 of the booster plunger I1, where itacts against the end of the internal bore 22 within the main plunger 2|,causing the latter to move rapidly to the right, carrying with it thedie carrier I4 and the die 29.

As the main plunger' 2| advances fluid is drawn through theeheck valve|58 and line |66 from the tank |6|. It will be understood, however, thatthe check valve |59 may be immersed in the tank 6|. This uid is drawninto lthe space within the cylinder bore 26 to the left of the mainplunger 2|, causing this space to be filled with oil. When the mainplunger 2| advances to casacca a predetermined position, the die carrierMaengages a control rod |54, which shifts the valve |54 when the twodies 29 and 36 are almost together. The shifting of the valve |54 admitspressure, through the line |53, the valve |54, the line |55 and the port|56 to the left-hand end of the main cylinder 26. acting against the endofthe main plunger 2| and causing the full force of the plunger to Abeexerted against the dies 29 and 36. The die assembly continues to moveto the. right, pushing the die head |5 and the rods 43 to the rightuntil the socket 46, leading to the die 36, is nrmly pressed against thetip 19 of the injection nozzle 16 (Figures l and 2). The full force ofthe main plunger 2| is not exerted against the nozzle 16, however,because the die head l5. is now cushioned against the pistons 52 as soonas they are engaged by the enlarged heads 5| of the plungers 43. Thisengagement takes place slightly before the nozzle 16 is engaged by thesocket 46.

Meanwhile, pressure fluid has been flowing through the line |16 to theports'55 leading into the cylinder bores 53, thereby tending to forcethe piston heads 52 to the left. In this manner the pistons 52 combineto oppose the pressure exerted by the main plunger 2|. The force exertedby the pistons 52 does not subtract from the total force used to clampthe dies 29 and\36, but merely reduces the force exerted against the endof the nozzle 16. Since the pistons 52 are not connected to the plungers43, the latter trave1 rapidly until they engage the former. Thisconstruction, moreover, permits the use of a small travel of the die 36which engages the nozzle 16, hence, saves time inclosing the dies 29 and36. Obviously, a saving in the time of closing the dies operates to savetime in the opening thereof.

With the dies 29 and 36 now closed and in engagement with the injectornozzle 16, the injector operating valve y|82 is shifted to admitpressure from the line |8|, into the line |86 and port 51 leading intothe cylinder bore 58 to the right of the piston head 59. This forces thepiston 59, piston rod 6,6 and injection plunger 61 -to the left in aninjection stroke, thereby filling the dies with plastic material. Theelectrical control system for the feeding apparatus of the injectoroperates inthe manner previously described, in response to theengagement of the limit switches |I5 and ||6 (Figure 3) by the cam 66 onthe injection plunger 61.

When the piston 52 first starts to move it encounters a comparativelylow resistance, hence, this causes a drop in pressure in the lines |86and |81 leading to the line |66. The check valve the injector operatingvalve |82 is again shifted Y so that pressure uid is admitted throughthe line |85 to the spaceon the left-hand` side of the piston 59,thereby returning the injector plunger 61 to its retracted position. Atthis point additional material is fed into the injector chamber by thefeed screw 89, in accordance with the electrical operation previouslydescribed.

After a sufficient time has elapsed for the material to cool in thedies, the dieclamping valve |52 is shifted to its opposite position sothat pressure fluid is discharged from the line 468, through the valve|52, the line |12 to the port |13, into the space at the right-hand endof the main cylinder bore 2l, returning the main plunger 2| to itsstarting position and separating the die halves 29 and 30. As Vthe diecarrier i4 reaches its retracted position, the knock-out rods 33 andknock-out bar 32 operate to cause the pins 34 to` eject the work-piecefrom the die.

It will be understood that we desire to comprehend within our inventionsuch modifications as comev within the scope ofthe claims and theinvention. l

Having thus fully described our invention, what We claim new and desireto secure by Letters Patent, is:

1. In a material-supplying device for a plastic molding machine, aninjector for plastic material having an elongated chamber and aninjector plunger operable therein, a feeding chamber disposed obliquelyof said injector chamber and opening therein, and a feeding screwrotatable in said obliquely disposed chamber at an oblique axisrelatively to the axis of said injector plunger for positively feedingmolding material to said injector.

2. In a material-supplying device for a plastic molding machine` aninjector for plastic material having an elongated chamber and aninjector plunger operable therein, a feeding chamber disposed obliquelyof said injector chamber and opening into said injector chamber near theend of said injector plunger in its retracted position, and a feedingscrew rotatable in said obliquely disposed chamber at an oblique axisrelatively to the axis of said injector plunger for positively feedingmolding material to said injector.

3. Ina material-supplying device for a plastic molding machine, aninjector for plastic material having an injector chamber and an injectorplunger operable therein, means for supplying molding material to saidchamber, a .feeding chamber connected to said injector chamber andextending between said supplying means and injector chamber, a feedingmember movable in said feeding chamber for forcefully feeding materialfrom said supply means to said injector chamber, a motor connected tosaid feeding member, and adjustable timing means for effecting theoperation of said feeding member motor for periods of time of apredetermined duration whereby to feed a corresponding predeterminedquantity of molding material to said injector chamber.

4. In a material-supplying device for a plastic molding machine, vaninjector for plastic material having an injector chamber and an injectorplunger operable therein, means for supplying molding material to saidchamber. a feeding chamber connected to said injector chamber andextending between said supplying means and injector chamber, a feedingmember movable in said feeding chamber for forcefully feeding materialfrom said supply means to said injector chamber, a motor connected tosaid feeding member, adjustable timing means for effecting the operationof said motor for periods of time of a predetermined duration, and meansresponsive to' the motion of said injector plunger for initiating theoperation of said timing means whereby to feed a correspondingpredetermined quantity of molding material to said injector chamber fora stroke of said injector plunger.

5. In a material-supplying device for a plastic K molding machine, aninjector for plastic material having an injector chamber and an injectorplunger operable therein, means for supplying molding material to saidchamber, a feeding chamber connected to said injector chamber andextending between said supplying means and injector chamber, a feedingmember movable in said feeding chamber for forcefully feeding materialfrom said supply means to said injector chamber, an electric motorconnected to said feeding member, and electrical means responsive to apredetermined motion of said injector plunger for energizing saidelectric motor a predetermined period of time to move said feedingmember a predetermined amount whereby to feed a predetermined quantityof molding material to said injector chamber for a stroke of saidinjector plunger, said electrical means being arranged to energize saidmotor for such period of time as to feed a slightly excessive quantityof molding material to said injector chamber per stroke of said injectorplunger, said electrical means and said motor being arranged to remaintemporarily unenergized ,after an incomplete stroke of said injectorplunger resulting from the accumulation of molding material in saidinjector chamber exceeding a predetermined quantity.

6. In a material-supplying device for a plastic molding machine, aninjector for plastic material having an injector chamber and an injectorplunger operable therein, means for supplying molding material to saidchamber, a feeding chamber connected to said injector chamber and.extending between said supplying means and injector chamber, a feedingmember movable in said feeding chamber for forcefully feeding 4materialfrom said supply means to said injector chamber, an electric motorconnected to said feeding member, and electrical means for moving saidfeeding member a predetermined amount for feeding a predeterminedquantity of molding material to said injector chamber slightly in excessof the capacity thereof, said electrical means being energizable solelyin response to the substantial completion of a full working stroke ofsaid injector plunger and adapted to remain deenergized upon anincomplete working stroke thereof by reason of the temporaryaccumulation of an excessive quantity of molding material in saidinjector chamberwhereby to constantly insure an adequate supply ofmolding material for said injector chamber by temporarily rendering saidfeeding member inoperative.

7. In a material-supplying device for a plastic molding machine, aninjector for plastic material having an injector chamber and an injectorplunger operable therein, means for supplying molding material to saidchamber, a feeding chamber connected to said injector chamber andextending between said supplying means and injector chamber, a feedingmember movable in said feeding chamber for forcefully feeding materialfrom said supply means to said injector chamber, electrical means formoving said feeding member, an electric circuit connected thereto, and alimit switch connected in said circuit, said limit switch beingoperatively engageable by said injector plunger for controlling theenergization of said circuit.

8.. In a material-supplying device for a plastic molding machine, aninjector for plactic material having an injector chamber and an injectorplunger operable therein, meansy for supplying molding material `to saidchamber. a feeding chamber connected to said injector chamber andextending between said supplying means and injector chamber, a feedingmember movable in said feeding chamber for forcefully feeding materialfrom said supply means to said injector chamber, an electric circuitconnected thereto, time-responsive means for operating said feedingmember a predetermined time, and a limit switch responsive to the motionof said injector plunger for controlling the energization of saidcircuit. l

9. In a material-supplying device for a plastic ber, electrical meansfor moving said feeding member, an electric circuit connected thereto,

time-responsive means for operating said feeding member a predeterminedtime, and a plurality of switches operated by the motion of saidinlector plunger for controlling the energization of said circuit, saidswitches being operated by said molding machine, an injector for plasticmaterial having an injector chamber and an injector plunger operabletherein| a feeding chamber connected to said injector chamber, a feedingmember movable ln said feeding chamber, means for supplying moldingmaterial to said feeding member, electrical means for moving saidfeeding member, an electric circuit connected thereto, time-responsivemeans for operating said feeding member a predetermined time, and aplurality of switches operated by the motion of said injector plungerfor controlling the energiplunger at separated locations, saidtime-responsive means being arranged to feed to said injector chamber aquantity of material slightly in excess of the capacity thereof, one ofsaid switches being inoperable by said plunger when the accumulatedmaterial exceeds a predetermined quantity whereby tolrender said feedingcircuit temporarily inoperative during the motion of said plunger ininjecting said excessive quantity into said die.

WALTER ERNST.

IRA B. LAWYER.

